ghostscript update, libspectre and #840691 (regression caused in evince, zthura-ps, ...)

[Salvatore Bonaccorso]

Hi libspectre maintainers,

Did any of you had a chance to look at #840691? It is currently still
assigned to src:ghostscript, but the problem might actually lie in
libspectre.

Thanks already for your help,

Regards,
Salvatore